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The Inconvenient Truth about Tsunamis


For a tsunami to occur, an earthquake must exceed a certain threshold. The 8.9-magnitude (on the Richter Scale) of Japan's earthquake was enough to trigger a tsunami, and the magnitude-7.7 earthquake that struck Indonesia in October 2010 only just surpassed the threshold for causing a tsunami. Earthquakes below 7.5 or 7.0 usually do NOT trigger tsunamis. A 7.1 or a 7.4 will not do it. In our whole history of colonial settlement post 1840, only 2 earthquakes have exceeded 7.7mag, and that occurred in 1855, in Lake Wairarapa, a 8.2mag. (ref: and 2017, in Kaikoura.

Even that is uncertain, because the Richter Scale was only developed in 1935. So magnitude of seismic events prior to that is only estimation. The fact remains that in our nearly 200 year history of settlement, over 2 million earthquakes have been recorded, and from them less than a single handful of tsunami scares, with little or no loss of life. Compare that to the annual tragic road toll of several hundred lives lost. It is disproportionate. We have extensive tsunami alarm systems in place costing ratepayers thousands of dollars e.g along the Kaikoura coastline, but there are few road risk alarm systems in place.

Therefore NZ very seldom, and in truth almost never, gets events large enough. On the other hand, Japan, which is the world's most active earthquake region regularly gets such larger events. Once a tsunami reaches shallow water near the coast, it is slowed down, yet NZ is almost surrounded by a shallow shelf. e.g. an underwater layer that is the edge of the plate on which Australia and NZ sits extends out to the east at Wairarapa by about 200miles before dropping off into the deep Pacific. In comparison, Japan quite quickly drops into the deep Pacific.

In the Pacific Islands the currents go east, so higher waves from the Samoa tsunami could not threaten NZ. Earthquakes that occur around our coast are not able to threaten to travel inland with any destructive force. The speed of tsunami waves (and therefore the destructive power) depends on ocean depth rather than the distance from the source of the wave. One that is 55kms deep (Friday's event) is even less likely to cause harm. To get some perspective on this, consider that the 2004 Indian Ocean event was 10kms down, the Samoan tsunami (magnitude 8.0) was at a depth of 18 km, and the 11 March 2011 Japanese tsunami was an 9-mag at the depth of 32kms.

Tsunami scares are part of the funding industry that makes up alarmist scenarios to achieve research funding. They are alongside other scams like global warming, climate change and rising sea levels. The media have now created widespread public panic that every earthquake is a potential tsunami, every summer warm spell is the result of runaway global warming, and every dry season is proof of climate change. I believe that this is irresponsible science, and should be condemned as child abuse, for children have now been whipped into a state of permanent fear.

When I was a child I did not ever hear the word 'tsunami'. But it was probably not that they did not occur then. We might reflect that tsunami is a Japanese word, and was only applied to events in Japanese waters. In a similar way, only the northern hemisphere gets "hurricanes", and only the Asian countries get "typhoons". Down here we call them cyclones. And in Japan they have always had tsunamis associated with large earthquakes because the depth of the Pacific juxtaposing with the largest land mass; Eurasia, causes them. So why have they apparently become more frequent worldwide in more recent years?

The only thing that has changed has been the level of media scaremongering. Now it is just one more thing we can add to the list of things that can 'get' us, that list including earthquakes, cyclones, droughts, floods, planet warming, planet cooling, Bird Flu, Sars, sea level rise swamping all the cities, oceans turning to acid, and plastic supermarket bags destroying the oceans.
According to , in the 84 years between 1929-2013, worldwide there have been 25 registered tsunamis. They are listed below. In the first 40 years, to 1960, 9 or 10 had occurred. In the next 40 years to 2000, another 9 or 10. But in the last decade there have been a whopping 6. What has happened? During the 13 year gaps between 1933-1946 and between 1964-1976 no tsunamis were recorded. Now tsunamis are showing up almost every year.
It is because every time there is a large earthquake the media are now poised, salivating, hoping for a tsunami so they can gleefully report a certain number of deaths. This hoping makes it a media reality. Now even no tsunami is called one. The 20cm wave that arrived on NZ shores in September 2015 was called a "small tsunami". But there is no such thing as a small tsunami. By definition a tsunami is a huge destructive wave. 
Yes, Chile had one. NZ didn't.

Tsunamis recorded to 2013
1. Grand Banks  Atlantic Ocean off the south coast  129 km/h (80 mph) Nov 18, 1929  
2. Sanriku  Sanriku-kaigan, Japan 10 meters, height 2 kilometers long Mar 2, 1933
3. Aleutian Islands  Aleutian Islands, Alaska   Apr 1, 1946 
4. Severo-Kurilsk Pacific Ocean, Kamchatka 15–18 meters (49–59 ft) Nov 5, 1952 
5. Lituya Bay megatsunami Panhandle near Alaska, USA 30 metres (100 feet)  Jul 9, 1958 
6. Valdivia  Coast of South Central Chile 10.7 m (35 ft) waves measuring up to 25 meters high May 22, 1960 
7. Vajont Dam North of Venice, Italy 110 kilometres per hour (68 mph) Oct 9, 1963
8. Niigata  Honshu island, Japan (Niigata)   Jun 16, 1964 
9. Alaskan  South-Central Alaska ( USA) 100 feet (30 m) Mar 27, 1964 
10. Moro Gulf  Moro Gulf in Southern Mindanao( Philippines) 4 to 5 metres (13 to 16 ft) August 16, 1976 UTC August 17, 1976 
11. Tumaco  Tumaco, Colombia Three to four waves Dec 12, 1979  
12. Sea of Japan  Oga Peninsula (Sea of Japan) 10 meters (33 ft) May 26, 1983
13. Nicaragua  West Coasts of Nicaragua and Costa Rica 9.9 meters high Sep 2, 1992
14. Hokkaido  Okushiri Island (Sea of Japan) Maximum run-up of 32 M, 3.5 m at Akita in northern Honshu, Jul 12, 1993
15. Java  Coast of Indonesia 14 m (46 ft) east Java coast and up to 5 m (16 ft) Jun 3, 1994 
16. Papua New Guinea  Papua New Guinea Estimated at being 15 m (59 ft) high with an average height of 10.5 m (34 ft) Jul 17, 1998 
17. Indian Ocean - Sumatra Indian Ocean (Indonesia) 50 M 26. Dec. 2004 
18. Pangandaran  South Coast of Java Island, Indonesia South Java coast saw runup heights of 5–7 meters (16–23 ft),peak surge 69 ft, 17. Jul. 2006 
19. Kuril Islands  Kuril Islands Estimated tsunami waves to be as tall as 2 metres 15. Nov. 2006
20. Solomon Islands  Ghizo Island, in Solomon Islands 12 m (36 feet) 2. Apr. 2007 
21. Samoa  Samoan Islands 14 metres (46 ft) 29. Sep. 2009 
22. Chile  coast of Chile, Argentina 2.34 m (7.68 ft)  27. Feb. 2010 
23. Sumatra  Western Coast of Sumatra,Mentawai Islands (Indonesia) 3 m (9 ft) 25. Oct. 2010 
24. Tohoku  East Coast of Tohoku (Japan) 2 m (6.6 ft) 11. Mar. 2011 
25. Solomon Islands  Lata, Solomon Islands 1 metre (3 ft 3 in) 6. Feb. 2013

Finally, we punish children who do not tell the truth. Yet adults are pushing this watch-out-for-tsunamis barrow as if tsunamis could occur daily anywhere, and no one is stopping the falsehood. Obviously tsunamis are a danger in certain countries and for them it is worthy to teach caution. But countries that have not experienced tsunamis will continue to not experience them.
The precautionary principle is fine if it is a function of truth and probability. But the moral of The Emperor's Clothes was about precaution against bullshit.

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